Rukmini Callimachi and Middle Eastern ruins.

Rukmini Callimachi hosts the New York Times podcast Caliphate.

Photo illustration by Slate. Photos by Nicola Gell/Getty Images for SXSW and Zaid Al-Obeidi/AFP/Getty Images.

Six episodes into a 10-episode series, the New York Times' podcast Caliphate is a handsomely produced collection of riveting audio in search of a stable identity. In the podcast's short prologue, the Times reporter Rukmini Callimachi tells producer Andy Mills that her mission is to answer the question "Who are they?"—meaning the Islamic State, Callimachi's beat. But is Caliphate a news podcast, like the Times' hugely popular The Daily, in which host Michael Barbaro interviews the journalists responsible for the paper's biggest stories of the moment—with Mills as Barbaro and Callimachi as the reporter conveying her scoops? Or is it, as its limited run suggests, a story, with a beginning, middle, and end?

The Daily works so well because it's symbiotic with the paper. Listeners feel like they've been seated next to the reporter at a dinner party and are getting both the tl;dr version of a six-column feature and a bit of the reporter's personality and attitudes. Without the institutional rigor of the Times behind it, however, all this insider talk would be little more than gossip, yet another take in a world brimming with free-floating opinions.

The Daily has the luxury of picking and choosing from amid all the beat reporters in the Times, plucking each one out when she has a story to tell. Caliphate doesn't: It's committed to one beat, even if it's approaching it, as a beat reporter does, from many angles. But news is news because nobody knows how it will turn out. Serial demonstrated how difficult it is to reconcile the two formats. An investigation that unfolds in real time is an investigation that may not reach a definite conclusion. Because it couldn't really tell us who killed Hae Min Lee, as Serial progressed, it became less about the facts than about what Sarah Koenig, its narrator, made of them. Its ultimate subject was Koenig herself.

The first episode of Caliphate sounds a lot like a news podcast. Mills plays Dr. Watson to Callimachi's Sherlock Holmes, following her around, armed with a mic instead of a trusty service revolver. War correspondents have always cut romantic figures; this holds true even at a time when public opinion of journalists has never been lower. Earlier this year, Callimachi hit reportorial pay dirt by going through sites that had been liberated from retreating ISIS forces, filling up plastic garbage bags with abandoned documents, laptops, and other potential sources of inside information. Mills recorded her doing this as mortar fire sounds in the distance. "I am looking for ISIS's diary," says Callimachi, her soft voice laced with the heedless avidity of a natural-born sleuth, "their internal correspondence and receipts. Their personal tiffs with co-workers that end up getting sent to the equivalent of ISIS HR. The things they're struggling with and writing letters back and forth about."

Like Holmes, Callimachi doesn't think of herself as a badass, although listeners are plainly meant to. She's too obsessed with getting the goods. The podcast needs Mills to provide the perspective of an ordinary witness, the guy who marvels at Callimachi's willingness to put herself in danger by following so closely behind the front line of the battle. All of this signals to the listener that Caliphate is about Callimachi: what it's like to cover an infamously savage terrorist operation and what sort of person would choose to do so. The episode closes with Callimachi telling an anecdote about being visited by the FBI at her home in the states. They warned her that she has been named by ISIS in a "targeted threat." Weeks later, a late-night knocking at her door prompted her to phone 911. The podcast includes a recording of her call to an operator who obviously has no idea who Callimachi is or why this lady thinks ISIS would be targeting her suburban home. (It turned out to be someone from the water department.) Callimachi is sheepish about the incident. "They're trying to scare us, to make themselves into boogeymen and live in our imagination," she says. "And that night, they got me." Most of the time, apparently, they don't.

In Episode 2, however, Caliphate is hijacked by an interview. "Abu Huzayfah" is the nom de guerre used by a young Pakistani-Canadian recruit whom Callimachi found through his postings on Instagram. (Reporters covering ISIS often track sources and subjects through social media because the group, its recruiters, and its admirers are so active there.) Abu Huzayfah, much to Callimachi's surprise, agrees to an in-person interview in a hotel in Canada. He is astonishingly frank, answering every question in detail, describing how he became interested in the jihadi cause after the invasion of Iraq and was motivated to join ISIS by the civil war in Syria. What she finds particularly exciting about him as a source is that he was a member of ISIS's local police force, carrying out sentences and executions. All of her previous sources had told her they'd "witnessed an execution, witnessed a beheading, or been present when a stoning took place, but they never took part in it themselves," she tells Mills. "They were a cook, a driver, a translator. They present themselves as being witnesses to horror but never as carrying out the horror themselves."

Whether those sources were downplaying their own involvement or not isn't clear, but if so, that wouldn't be unusual. Convicted murderers, even those who admit to their crimes, often distance themselves from the act, claiming not to understand why they did what they did or saying that they can barely remember doing it. Abu Huzayfah is remarkable for the unflinching way he talks about what it was like to be spattered with blood while flogging a man (for not making sure his wife was appropriately covered in public), to shoot a tribal elder for defying ISIS on its march toward Baghdad, and finally to stab a man to death, ISIS's ordained punishment for selling drugs. When he describes the sights, sounds, and smells of these acts, how sick they made him—particularly the stabbing, which ultimately drove him to escape from ISIS-held territory—Abu Huzayfah's account is vivid and wrenching but also free of excuses, histrionics, or equivocation. He sounds like your friend's gawky, impressionable teenage brother, which as Callimachi points out is what makes people like him so "spooky."

Callimachi's interview with Abu Huzayfah takes the better part of three episodes of Caliphate, and you can see why. In a single source she has found the epitome of ISIS's Western recruits: a middle-class kid, a fan of video games and Star Wars, from a moderately religious family (his mother and sister are unveiled), who did not feel discriminated against in Canada. "They're living a pretty good life here," he says of his parents. "Me, I always wanted something bigger, not something simple and boring." He longed for adventure, purpose, to be tested like the heroes in the pop culture he loved. Jihadi propaganda capitalized on these yearnings, giving him a community to identify with and defend—Muslims under attack in their homelands—and a cause to which he could devote his life. Even if he died, he says, "I'll die fighting for what I believe in. I'd die as a hero then. I'd die doing something."

But as compelling as this interview is, it represents a major detour from the initial focus on Callimachi and her reporting. Is this her story or his? Podcasts rely so heavily on the human voice—and our connection to them is so intimately tied to that voice—that they will inevitably seem to be about whoever does the most talking. Only in the sixth episode does Caliphate return to the challenges of covering ISIS, when Callimachi finds troubling inconsistencies between Abu Huzayfah's account of his movements in 2014 and the stamps on his passport. (He has since come under investigation in Canada and now denies killing anyone.) She and a team of Times staffers mobilize to corroborate what he's told them: drawing up timelines on conference room whiteboards, phoning colleagues with contacts in the national security agencies who can be persuaded to say whether he's on any no-fly lists, enlisting a stringer in Pakistan to interview the family he claims to have stayed with there. They even consult an expert on "geolocation" who can examine a photo of a masked man shooting a gun into the Euphrates river and tell you not only precisely where it was taken but when. So now Caliphate has shifted again: This is no longer the tale of a lone journalist braving shells and gunfire to ferret out ISIS's secrets. Callimachi may be the dogged leader of the effort, but now Caliphate is an ensemble piece, the story of a formidable journalistic institution bringing to bear a phalanx of experts as freakishly competent as the forensic specialists on CSI.

With four episodes to come, will Caliphate pivot yet again? As engrossing as each episode is, the series feels unshaped, steered in a new direction every time a new development materializes. That's how a great newspaper covers a beat, and there's much to be said for it. But the grandeur of Caliphate's title holds out the promise of a bigger, more coherent picture of the Islamic State, one the podcast has yet to deliver. In the end, it may prove as elusive as the Islamic utopia from which it took its name.